Method for controlling a drivetrain of a vehicle

ABSTRACT

A method for controlling of a drive train of a vehicle having a multi-group transmission, an output mechanism and a control apparatus for the regulation of the drive train. The multi-group transmission consists of an automatic transmission and a range group. To change the ratio of the range group the drive train is relieved of load; a shifting element of the range group is closed; a shifting element of the range group is synchronized and opened; and a ratio of the automatic transmission is so altered that a change of the ratio of the multi-group transmission is less than in a case of an individual alteration of the ratio of the range group.

This application is a national stage completion of PCT/EP2003/009123filed Aug. 18, 2003 which claims priority from German Application SerialNo. 102 38 126.7 filed Aug. 21, 2002.

FIELD OF THE INVENTION

The invention concerns a procedure for the control of a drive train of avehicle.

BACKGROUND OF THE INVENTION

Drive trains of vehicles, especially of all-terrain vehicles, whichpossess at least one driving machine, one multi-group transmission andone output drive, have been known in the practice for a considerabletime. The formation of a drive train with a multi-group transmission isundertaken when a multiplicity of gear stages with the fewest possiblegear pairs is to be made available.

Multi-group transmissions, in general, incorporate a combination of aplurality of individual transmissions grouped in a series arrangement.The transmission groups can be designated as the so-called forwardshifting groups (in order of power flow), a main transmission and aso-called after-shifting groups, which are known as range groups. If amain transmission of a multi-group transmission is constructed as anautomatic transmission, then a greater degree of driving comfort is madeavailable to a driver, in that a multitude of gear stages becomeavailable. Such an automatic transmission can be comprised of six gearstages for forward travel and one gear stage for reverse movement.

Range groups are characterized, when present as transmission groups ofmulti-group transmissions, in that an input speed of rotation to therange group is always in the “slow” stage, where a substantial increasein torque takes place simultaneously. Because of the high torqueincrease, range groups in a multi-group transmission are always placedto follow in a following position in regards to the main transmission,in order to avoid running the exceedingly high torque through the maintransmission.

Constructively applicable formations of range groups in practice,include the use of either counter forward transmission groups orplanetary gear transmissions, wherein the latter design offers a morecompact alternative and has the advantage of lesser installation space.

A change of a ratio in a range group is executed by a shifting element,whereby shifting can be made between a first ratio “low” and a secondratio “high”. With this arrangement, and when in a first selected lowgear of the range group and in combination with the main transmission,the driver has a choice of ratios available, which are an advantage foroperation of a vehicle in a terrain characterized by steep climbs andwherein slow vehicle speeds are acceptable.

The second ratio “high” is less subject to losses, so that whentraveling under normal condition of terrain and also at higher drivingspeeds, shifting into the second ratio “high” is to be preferred.

Experience in actual practice has indicated that where conventionalprocedures for control of a drive train are concerned, a disadvantage ispresent, i.e., a gear stage of a multi-group transmission demanded by anactivated shifting program, is formed through a combination of a ratioof the main transmission and the ratio “low” of the range group, eventhough the demanded ratio of the multi-group transmission could also beachieved by a combination of the ratio “high” of the range group and acorresponding ratio of the main transmission; this being in order toavoid the transfer of a higher torque through the main transmission.

The purpose of the present invention is to provide a method for thecontrol of a drive train of a vehicle available by which a multi-grouptransmission can be driven at a high degree of efficiency.

SUMMARY OF THE INVENTION

In the case of the method according to the invention, wherein acurrently activated shifting program is subject to being subordinated byan operational strategy, i.e., a shifting strategy, in an advantageousmanner, there is automatically executed a change of the ratio of therange group and simultaneously in the automatic transmission a favorablecounter-shift takes place so that a speed of rotation difference betweenthe automatic transmission and the range group is minimized.

The shifting procedures of the multi-group transmission are thus, in anadvantageous manner, carried out completely automatically via anappropriate control of the automatic transmission and of the rangegroup, whereby the driver of a motor vehicle is freed of involvement.

Furthermore, it is of advantage that the selection of the ratio of therange group via the superimposed operational strategy is carried out insuch a manner that “unacceptable” combinations cannot occur, i.e.,combinations of the ratios of the multi-group transmission giving a poordegree of efficiency cannot be caused by combining one inappropriateratio of the automatic transmission and one inappropriate ratio of therange group.

By the term “unacceptable” or “poor degree of efficiency” of themulti-group transmission combinations, which bring about undesirableefficiency, is to be understood any combination of the individual ratiosof the automatic transmission and of the range group wherein very highinput speeds of rotation are delivered to the range group. This is thecase, for example, in the range group, if a ratio for the a highlyincreasing torque is generated while, at the same time in the automatictransmission, a small ratio must accordingly be applied to create ademanded ratio of the multi-group transmission from the shifting programin order to be able to achieve a higher level of vehicle speed. Suchratio combinations are, however, very conducive to losses and, on thisaccount, are to be avoided.

First, in a case of a combination of a given low ratio of the automatictransmission with a high ratio of the range group, a very high speed ofrotation may occur in the range group, which acts to reduce the degreeof efficiency of the multi-group transmission. Second, to offset this,the ratio in the range group is altered in the direction of a smallerratio for the attainment of a currently desired ratio of the multi-grouptransmission. At the same time, a higher ratio is automatically set toachieve the demanded ratio of the multi-group transmission in theautomatic transmission.

When this is done, then the input speed of rotation of the range groupis advantageously reduced and the range group goes into “high”operation, whereby the degree of efficiency of the multi-grouptransmission is substantially improved. This leads, in turn, to areduced development of heat in the range group as well as to a reductionof the consumption of fuel for the vehicle, i.e., for the motor.

In an advantageous variation of the method, according to the invention,provision is made that in a ratio change of the range group, asynchronization of a closable shifting element of the range group by acontrolling action on shifting elements of the automatic transmission iscarried out. Thereby, the possibility exists to eliminate mechanicalsynchronization in the range group in an advantageous way, either forseparate, individual components or integrated into the range group as awhole. Thus advantageous possibility is at hand to construct a rangegroup having a lesser complexity of design than is the case incomparison to the multi-group transmissions as made by conventionalpractice. Furthermore, such a range group transmission permits aconsiderably smaller installation space.

In addition, the synchronization of the range group transmission, via achange of its ratio being brought about by the automatic transmission,offers the advantage that the shifting elements of the range group canbe constructed as shape-fit shifting elements, preferably as dogclutches. Such shape-fit shifting elements can transfer high torques, asmaller installation space is required and thereby lesser manufacturingcosts are incurred.

An additional, advantage is that by the omission of the mechanicalsynchronization in the range group, a reduction of mechanicalsynchronizations of the range group, brought about by traction torqueoccurs, whereby heat development in the range group is considerablyreduced. In the case of mechanical synchronization, the traction torquearises essentially by liquid viscosity, which arises between thefrictional layers of disk clutches or brakes, where the fluid isgenerally oil.

An additional essential advantage of the invented procedure is that byway of the synchronization of the range group by way of the automatictransmission, traction interruption time is considerably reduced fromthat commonly known in the conventional method of the present daypractice. This is due to a change of input drive speed of rotation ofthe motor according with a need can be accomplished in a short time in aplain and simple manner via an appropriate control of shifting elementsof the automatic transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings in which:

FIG. 1 is a schematic presentation of a drive train with a motor, astarting element and a multi-group transmission consisting of anautomatic transmission and range group;

FIG. 2 is a schematically presented selective lever for an automatictransmission with a shift-selector, which exhibits an off-road position;

FIG. 3 is a bar chart in which ratios of a multi-group transmission arepresented in relation to the ratios of an automatic transmission and arange group;

FIG. 4 is a diagram wherein for individual gear stages of a multi-grouptransmission, in accord with FIG. 3, is respectively shown a curve ofthe velocity of a vehicle in relation to the motor speed of rotation;

FIG. 5 is several curves of torque vs time, which occur during a changeof a ratio in the range group of the multi-group transmission inrelation to components of the drive train as shown in FIG. 1,

FIG. 6 is a chart showing speed of rotation vs time curves, whichcorrespond to the torque vs time curves appearing in FIG. 5;

FIG. 7 is an additional embodiment example of an automatic transmissionselection lever, which is combined with a shift-selector for the demandof a ratio of the range group;

FIG. 8 is a bar chart in which different gear stages of a multi-grouptransmission are presented; the stages are controlled by the automatictransmission selection lever and the selection means in accord with FIG.7;

FIG. 9 is a diagram in which, for each individual gear stages of amulti-group transmission in accord with FIG. 8, a curve is presented ofa vehicle velocity vs a speed of rotation of the motor;

FIG. 10 are several curves of torque vs time, which occur during achange of a ratio as shown in FIG. 9, in the range group of themulti-group transmission affecting components of the drive train inaccord with FIG. 1; and

FIG. 11 are several curves of rotational speed vs time of components ofthe multi-group transmission, which correspond to the curves of torquevs time of FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic drive train 1 of a vehicle, preferably anall-terrain vehicle, which is not further described. The drive train 1consists of a motor 2, a start-up element 3 and a multi-grouptransmission 4. The driving machine is designed as an internalcombustion motor 2, the drive moment m_(mot) of which is transmittedthrough an output drive shaft 5 onto which is connected the start-upelement 3, which is preceded by a hydrodynamic torque converter 6.Additionally, the start-up element 3 is constructed with a controlledconverter clutch 7 with which the hydrodynamic torque converter 6 can bebypassed.

The multi-group transmission 4 which, series-wise in direction of powerflow, follows the start-up element 3 is assembled from an automatictransmission 8 and a subsequently connected range group 9, whereby theautomatic transmission 8 represents the principal transmission of themulti-group transmission 4.

The presented transmission combination of the multi-group transmission 4consists, as shown, of the load-switching automatic transmission 8 and adog clutch connected gear string with reduction gear stages, whichcomposes the range group 9 having automatic activation. Thistransmission combination is provided with an electronic control system,which is formed, first, from an automatic transmission controlapparatus; second, from a range group regulator and, third, from a motorcontrol device.

These three control devices, which are not explained in any greaterdetail here, are interconnected with one another and, accordingly,exchange the control signals of the drive train 1 among themselves. Byway of a coordinated control of the automatic transmission 8 and therange group 9, the constantly meshed range group 9 becomes synchronizedwith the automatic transmission 8. The synchronization of the rangegroup 9, i.e., the synchronization of that element of the range group 9which is to be shifted, is carried out by an appropriate control ofshifting elements A to E of the automatic transmission 8.

The automatic transmission 8 possesses a first planetary gear set 10,wherein an internal gear 11 of this first planetary gear set 10 isconnected to the start-up element 3. More than one planetary gears rollbetween the internal gear 11 and a sun gear 12 of the first planetarygear set 10 and are rotationally guided on a planetary gear carrier 13.The planetary gear carrier 13 of the first planetary gear set 10 isconnected to the shifting element A as well as to the shifting elementB, whereby the shifting elements A and B are designed as frictional diskclutches.

The internal gear 11 of the first planetary gear set 10 is alsoconnected to the frictional disk clutch-type shifting element E. By wayof the shifting elements A, B and E, respectively, a connection can becreated between the first planetary gear set 10 and a second planetarygear set 14, which planetary gear set 14 can be designed as a doubleplanetary gear set, which essentially corresponds to a Ravigneaux-typeplanetary gear set.

The second planetary gear set 14 possesses a first sun gear 15 as wellas a second sun gear 16 whereby, between the first sun gear 15 and acommon internal gear 17, as well as between the second sun gear 16 andthe common internal gear 17, respectively, a plurality of planetarygears roll, which said planetary gears are rotatably secured by a firstplanetary gear carrier 18 or a second planetary gear carrier 19 of thesecond planetary gear set 14.

The sun gear 12 of the first planetary gear set 10 is firmly secured bybeing affixed to a housing 20 of the automatic transmission 8. Thesecond sun gear 16 of the second planetary gear set 14 is advantageouslybound to the transmission housing 20 by shifting element C, whichshifting element C is constructed as a friction disk brake. Moreover,the second planetary gear carrier 19 of the second planetary gear set 14can be immovably affixed to the transmission housing 20 by shiftingelement D, which, again is constructed as a friction disk brake or canbe directly connected to the transmission housing 20 as an alternate.

The common internal gear 17 of the second planetary gear set 14 is boundto a sun gear 21 of the range group 9 whereby, between the sun gear 21and an internal gear 22 of the range group 9, a plurality of planetarygears roll, which have been rotationally secured upon a planetary gearcarrier 23 of the range group 9, which is connected to the output drive.

For a presentation of a first ratio “low” of the range group 9, theinternal gear 22 of the range group 9 can be connected in such a mannerwith a transmission housing 20A of the said range group 9, by a firstshifting element 24, that the internal gear 22 is not rotatablyconnected with the transmission housing 20A of the range group 9. Asecond ratio stage “high” of the range group 9, located between theinternal gear 22 and the planetary carrier 23, is then actuated when thefirst shifting element 24 is opened, i.e., released and a secondshifting element 25 of the range group 9 is closed and the internal gear22 binds with the planetary carrier 23.

By an automatic transmission selection lever 26, as shown in FIG. 2, thedriver has several possibilities at his disposal. With this equipment,various positions “O”, “P”, “R”, “N” and “D” of the automatictransmission selection lever 26 are possible which, via a labeled notchscale, can be differentiated by the driver. In the “Position O” (i.e.,“off-road”) and in the “Position D” (i.e., “drive”) of the automatictransmission selection lever 26, a driving direction, respectively“forward travel” of the vehicle can be selected. The position “P” (i.e.,“park”) allows the vehicle to remain standing, whereby the output driveof the vehicle is blocked. The position “R” (i.e., “reverse”) permitsshifting into backward motion and in the position “N” (i.e., “neutral”)the flow of power of the drive train 1 from the motor 2 to the outputdrive of the vehicle is interrupted in the area of the multi-grouptransmission 4.

The positions “O” and “D”, associated functions of the automatictransmission selection lever 26 for forward travel, differentiatethemselves therein, in that by the chosen lever position “D” in therange group 9 the ratio “high” is established and, as shown in FIG. 3,makes ready for the driving operation of six gear stages, namely“III-H”, “IV”, “V”, “VI”, “VII” and “VIII” of the multi-grouptransmission 4 dependent upon the respective ratios “A1”, “A2”, “A3”,:A4”, “A5” or “A6” of the automatic transmission 8. The overall seriesof ratios of the multi-group transmission 4 then assumes the valueslying in a range of 4.17 to 0.69.

An intershift between the individual gear stages “III-H”, “IV”, “V”,“VI”, “VII” and “VIII” of the multi-group transmission 4 is carried outby a change of the ratio of the automatic transmission 8 which,advantageously, is in accord with a preselected or with a specifiedshifting program which, for example, has been input into the controlapparatus of the multi-group transmission 4 or the control of theautomatic transmission 8.

Should a driver choose the position “O”, by way of the above discussedselection lever 26, then by means of the multi-group transmission 4, itis possible to make use of gear stages “I”, “II” and “III-L” besides thegear stages “III-H”, “IV”, “V”, “VI”, “VII” and “VIII” of themulti-group transmission 4. The gear stages “I”. “II”, and “III-L” thenbecome available in the range group 9, if the ratio “low” is set and inthe automatic transmission 8, respectively, a first ratio “A1”, a secondratio “A2” or a third ratio “A3” is shifted into. A ratio of themulti-group transmission 4 then will be found within a range of 11.3 to0.69.

Furthermore, in the position “O” of the automatic transmission selectionlever 26, because of an operational strategy, which strategy issuperimposed on the respectively activated shifting program, at aparticular operational point of the drive string, a change isautomatically undertaken in the ratio of the range group 9 from theratio stage “low” into the ratio stage “high”. Simultaneously, in theautomatic transmission, a shift is made from the ratio “A3” to the ratio“A1”. The shifting procedures of the multi-group transmission 4 arecarried out entirely by an appropriate control of the automatictransmission 8 and the range group 9, whereby the driver of a motorizedvehicle is freed from this duty.

Continuing, the choice of the ratio “low” or “high” of the range group 9is governed by the superimposed operational strategy in such a mannerthat inappropriate ratio combinations of the automatic transmission 8and the range group 9 are prevented.

By “inappropriate” ratio combinations would be combinations of theindividual ratios of the automatic transmission 8 and the range group 9,wherein very high input speeds of rotation of the range group 9 exist.This could be the case in the range group 9, if the ratio “low” isselected and, in the automatic transmission 8, the ratio “A5” must beactuated in order to comply with a ratio of the multi-group transmission4 demanded by the shifting program.

Since, by a combination of a “small” ratio of the automatic transmission8 with the ratio “low” of the range group 9, a very high input speed ofrotation can occur in the range group, which would impair the efficiencyof the multi-group transmission 4 in order to obtain a respectivelydemanded ratio of the multi-group transmission 4, the ratio in the rangegroup 0 is altered from “low” to “high” and in the automatictransmission, automatically a “larger” ratio for the establishment ofthe required ratio of the multi-group transmission 4 is shifted into.Under these circumstances, the input speed of rotation of the rangegroup 9 is reduced and the range group 9 is operated in the “high”status, whereby the efficiency of the multi-group transmission 4 isclearly improved. This leads, in turn, to a reduced generation of heatin the range group 9 as well as to a reduction of fuel consumption ofthe motor 2 of the vehicle.

In order to carry out a shifting operation, i.e., a changing of theratio of the range group 9, which would be accompanied with the leastpossible interruption of traction, the change is to be undertaken duringa closely defined operating condition of the multi-group transmission 4of the drive train 1.

FIG. 3 shows a bar diagram, whereby the height of each respective barcorresponds to a respective quantitative value of the ratio of themulti-group transmission 4. The ratio of the multi-group transmission 4arises, respectively, from the combination of the ratio of the automatictransmission 8 and the ratio of the range group 9 and represents, againrespectively, one of the different gear stages, namely “I”, “II”,“III-L”, “III-H”, “IV”, “V”, “VI”, “VII” and “VIII” of the multi-grouptransmission 4.

In this matter, it is significant that the ratio of the gear stages“III-L” and “III-H” of the multi-group transmission 4, via anappropriate staging of the automatic transmission 8 and the range group9 are essentially the same. The two gear stages “III-L” and “III-H” ofthe multi-group transmission 4 are similar to all other gear stages ofthe multi-group transmission 4, because of a defined combination of theratios of the automatic transmission 8 and the range group 9. In thiscase, the gear stage “III-L” is established in the multi-grouptransmission 4 then in the automatic transmission 8, the ratio “A3” isset, further, simultaneously in the range group 9 the ratio “low” isshifted into. Different thereto, in a case wherein the gear stage“III-H” of the multi-group transmission 4 is actuated, then in theautomatic transmission 8, “A1” is selected and, in the range group 9,the ratio “high” is shifted into.

In the chosen position “O” of the automatic transmission selection lever26, upon the presence of a certain operational condition, shifting ismade in the range group 9 from “low” to “high” or in the oppositedirection. This operational condition is characterized in FIG. 4 by acircuit 30.

Because of the fact that the ratio of the multi-group transmission 4 inthe gear stages “III-L” and “III-H” are essentially equal, consequently,the curves of the same, wherein respectively vehicle speed v_(fzg), isplotted in FIG. 4 as ordinate and speed of rotation n_(mot) of the motor2 as abscissa, are practically identical. More closely defined, a speedof rotation n_(mot) of the motor 2 of the gear stage “III-L” correspondsat a certain vehicle travel velocity v_(fzg) approximately to the speedof rotation n_(mot) of the motor 2 of the gear stage “III-H”, thereverse being also true, of course.

In this condition of the operation of the drive train 1, if the ratio inthe range group 9 changes from “low” to “high”, then the actual changeof ratio can be executed in a very short time of interruption of thetraction, since the speed of rotation n_(mot) of the motor 2 during thechange of the ratio in the range group 9 remains practically the sameand only internal rotational inertias of the multi-group transmission 4need be mutually synchronized.

FIG. 4 might be entitled a “Rotary Speed vs Vehicle Speed Diagram”wherein the presented practically straight line curves respectively showthe vehicle speed v_(fzg) against the speed of rotation n_(mot) of themotor 2 at the various ratios of the multi-group transmission 4. Theratios of the multi-group transmission 4 are derived from thecombination of the ratio of the automatic transmission 8 and the ratioof the range group 9 which generates two ratio stages.

The individual curves are respectively designated by the letters “A” andone of the numbers “1” to “6”, which are given together in the ratiosset in the automatic transmission 8. Moreover, the letter following thenumber, namely “H” or “L”, whereby the letter “L” represents the ratio“low” and the letter “H” stands for the ratio “high” of the range group9.

In this way, the designation “A2H” makes it obvious that the designatedcurve of the vehicle speed v_(fzg) is set at a ratio of the multi-grouptransmission 4, which corresponds to the combination of the second ratio“A2” of the automatic transmission 8, and the ratio “high” of the rangegroup 9 and the ratio gear stage “IV” of the multi-group transmission 4.

From the “Rotary Speed vs Vehicle Speed Diagram” of FIG. 4 can beinferred that the curves of the vehicle travel speed v_(fzg) against therotational speed nmot of the motor 2 are nearly identical when, in theautomatic transmission 8 the ratio “A3” is set and simultaneously in therange group 9 the ratio stage “low” is shifted into or if, in theautomatic transmission 8, the ratio “A1” is shifted into and, in therange group 9, simultaneously, the ratio “high” is set.

With this information, it becomes clear that in connection with thepresentation in FIG. 3, that the change of the ratio stage in the rangegroup 9 from “low” to “high” or from “high” to “low” is particularly ofadvantage, simultaneously in the automatic transmission, if the ratio of“A3” is shifted into the ratio “A1” (or vice versa). The ratio of themulti-group transmission 4 remains, in such a case, essentially thesame, on which account, a combining speed of rotation of the motor 2compared to the desired speed of rotation of the multi-grouptransmission 4, with which the range group 9 is synchronized, isessentially the same as the speed of rotation of the motor 2 compared tothe ratio which is actuated in the multi-group transmission 4.

This means that upon a shifting of the ratio of the range group 9, amatching of the speed of rotation of the motor 2 is held up and asynchronization of the closable shifting element of the range group 9 aswell as the closable shifting element of the automatic transmission 8which, likewise, is carried out independently of the speed of rotationof the motor 2. This can be done in a very short time, namely from 0.1to 0.2 seconds or better to 0.15 seconds.

This provides a substantial shortening of the interruption time of lossof traction, especially when compared to conventional shiftingstrategies common in current practice. The conventional shifting canhave a duration of principally half a second up to one second, which isa substantial interruption of traction.

The curves “A5L” and “A2H” of the “Rotary Speed vs Vehicle SpeedDiagram” of FIG. 4, likewise, show that they are nearly identical. Theratio combination from the ratio “A5” of the automatic transmission 8and the ratio “low” of the range group 9 for the formation of the ratioof the multi-group transmission 4, however, would not be selected,because of the negative effects brought about by the superimposedoperational strategy, which was input into the control system and intothe respectively actuated shifting program.

Obviously, it lies within the judgment of the expert to speciallyexecute a change in the ratio in the range group 9 to meet requirementsof an existing application so that the change between the ratio stage“low” and the ratio stage “high” of the range group 9, when theautomatic transmission 8, the ratio “A5” or the ratio “A2” has alreadybeen engaged and, corresponding to the ratio change in the range group 9in the automatic transmission 8, a reverse shifting has taken place fromthe ratio “A2” toward the ratio “A5” (or vice versa).

In FIG. 5 is presented a plurality of torque curves within a shiftingtime t during a change of the ratio of the range group 9 from “low” to“high”. In this diagram, a curve m₂₄ represents the curve of the torqueapplied to the first shifting element 24 of the range group 9, whichoccurs during the shifting in the range group 9. A curve m₂₅ shows thetorque applied to the second shifting element 25 of the range group 9during the change of the ratio of the range group 9 from the ratio stage“low” to the ratio stage “high”.

Corresponding thereto is a curve m_(mot-e) of the motor 2, which sends asignal to the control apparatus and is designated as a so-callede-gas-moment. The e-gas-moment m_(mot-e) is that driving moment of themotor which, during the shifting, is applied to the multi-grouptransmission 4 on its motor-side and which is actuated by the controlapparatus. Additionally, a curve m_(mot-f) is shown, which depicts thecurve of a drive moment of the motor 2 instigated by the driver andwhich, during the ratio change in the range group 9, however, was notgiven consideration.

If a signal is given, because of a superimposed operational strategyinput into the control apparatus, to the end that for the relief of thedrive train in the range group 9, a shifting should be made therein fromthe ratio stage “low” into the ratio stage “high”, then the drive momentof the motor 2 in accord with the curve m_(mot-e) of the e-gas-momentfor the relief of the drive train 1, should be retained until the firstdog clutch shifting element 24, corresponding to the curve m₂₄, iscompletely relieved of load.

Subsequently, the e-gas-moment m_(mot-e), which is held constant untilthe complete relief of the first shifting element 24 is changed in thedirection of a positive value. After this, then the e-gas-momentm_(mot-e) is, to a certain extent, controlled up to the finalthrough-shift of the second element which is, likewise, designed as asecond shifting 25 in the range group 9. By this action, asynchronization of the second shifting element 25 is made possible.

From a defined point of time T_(ds), i.e., the elapsed time of shiftingof the second shifting element 25, the torque increases, as shown by thecurve m₂₅, which rises the torque of the second shifting element 25practically vertical, whereby the flow of power between the motor 2 andthe output shaft of the motor vehicle is restored. Simultaneously, amatch is made between the e-gas-moment m_(mot-e) and the driver momentm_(mot-f), whereby the procedure of the shifting, i.e., the change ofthe ratio in the range group, is completed.

The diagram of FIG. 6 shows a plurality of speed of rotation curves ofdifferent components of the drive train 1, in accord with FIG. 1, intheir state during shiftings in the range group 9 and in the automatictransmission 8, exhibiting the synchronizing of the range group 9 by wayof the automatic transmission 8, i.e., the synchronization of theshifting elements thereof, namely A to E. In these curves, the speed ofrotation n is plotted as ordinate over shifting time t as abscissa.

The various curves of speed of rotation of the individual components ofthe drive train 1 are respectively designated by the letters n and thereference numbers of the components of the drive train 1 are as shown inFIG. 1. Thus, for example, the curve n₁₃ presents the curve of speed ofrotation of the planetary carrier 13 of the first planetary gear set 10.

At the instant T₀, at which the shifting phase for the change of theratio of the range group 9 begins, the e-gas-moment m_(mot-e) ischanged, as may be seen in the curve presented in FIG. 5. This measure,which was introduced by the control apparatus has, at first, no effecton the rotational speed curves of FIG. 6, namely, curves n₁₃, n₁₅, n₁₆,n₁₇, n₁₈, n₁₉, n₂₂, n₂₃ and the curve of the motor 2 drive n_(mot). Withincreasing shifting time t, the torque m₂₄ of the first shifting element24 of the range group 9 is reduced to zero and the first shiftingelement 24 of the range group 9 is opened.

This means that the internal gear 22 of the range group 9 is releasedfrom its fixation on the transmission housing 20A of the range group 9and now becomes capable of rotation. From this point of time, therotational speed n₂₂ of the internal gear 22 of the range group 9gradually increases in the direction of the rotational speed n₂₃ of theplanetary carrier 23 of the range group 9.

From a point in time T₃, transfer capabilities for closing or opening,which belong to the automatic transmission 8, are so established thatreductions were made in the speed of rotation n₁₆ of the second sun gear16 of the second planetary gear set 14; the speed of rotation n₁₇ of thecommon internal gear 17 of the second planetary gear set 14; the speedof rotation n₁₈ of the first planetary carrier 18 of the secondplanetary gear set 14, and the speed of rotation n₁₉ of the secondplanetary carrier 19 of the second planetary gear set 14. The speed ofrotation n₁₃ of the planetary carrier 13 of the first planetary gear set10; the speed of rotation n₁₅ of the first sun gear 15 of the secondplanetary gear set 14 and the driving speed of rotation n_(mot) themotor 2 remain essentially unchanged.

The establishment of the capability of transfer of the shifting elementsof the automatic transmission 8 allows, in combination with thesignaling of the e-gas-moment m_(mot-e), a matching of the speed ofrotation n₂₂ of the internal gear 22 of the range group 9 to the speedof rotation n₂₃, until the speeds of rotation n₂₂ and n₂₃ are identical.At this moment, the second shifting element 25 of the range group 9 issynchronized and can be released or closed. This instant of time is moreexactly characterized in FIG. 6 by the term T₂.

At the point in time marked by T_(ds), a position sensor detects therelease of the second shifting element 25 of the range group 9 and thee-gas-moment m_(mot-e) is compared to the driver moment m_(motf).

Respectively, FIGS. 7 to 11 essentially represent the presentations ofFIGS. 2 to 6. With the aid of FIGS. 7 to 11 in the following, thebehavior of individual operational parameters of the drive train 1, asseen in FIG. 1, during the change of the ratios of the automatictransmission 8 and the range group 9, is described, whereby a control ofthe drive train 1 corresponding to one embodiment of the inventedprocedure is made, which is an alternative to the procedure as iscarried out in relation to FIGS. 2 to 6. For the sake of clarity in thedescription covering FIGS. 7 to 11, the same reference numbers are usedfor construction and functionally alike components as were so used inthe description covering FIG. 1 to FIG. 6.

FIG. 7 shows an automatic transmission selection lever 26 with the leverpositions marked “D”, “N”, “R” and “P”. With the automatic transmissionselection lever 26 is also a shift-selector 27 with combined choices ofeither “low” or “high”, by driver-side key-selection from the rangegroup 9. The shift-selector 27 is so connected with the controlapparatus of the drive train 1 that in a driver selection of theshift-selector 27, the respectively demanded ratio stage “low” or “high”shifts into the range group 9.

Dependent upon the respective ratio established in the range group 9,the individual gear stages “I”, “II”, “III”, “IV”, “V” and “VI” of themultigroup transmission 4 possess those ratios which are set forth in abar diagram in FIG. 8. The total height of one bar respectivelyrepresents a ratio of the individual gear stages “I”, “II”, “III”, “IV”,“V”, and “VI” of the multi-group transmission 4, if the selection “low”has been activated for the range group 9. The individual gear stages“I”, “II”, “III”, “IV”, “V” and “VI” of the multi-group transmission 4are respectively actuated by a corresponding change of the ratios of theautomatic transmission, whereby the respective ratio of the gear stages“I”, “II”, “II”, “IV”, “V” and “VI” of the multigroup transmission 4depends upon the ratio actuated in the range group 9.

In the range group 9, if the ratio stage “low” is in use then thoseratios are made available for the individual gear stage “I”, “II”,“III”, “IV”, “V” and “VI” of the multi-group transmission 4, which areindicated by the cross hatched bars of FIG. 8. This means that themulti-group transmission 4 in the ratio stage “low” of the range group 9possesses six gears, the ratio values which run between 11.3 and 1.87.In the range group 9, if the ratio “high” has been selected then themulti-group transmission 4, likewise, exhibits six gears, the ratiovalues which lie between 4.17 and 0.69.

FIG. 9 shows a speed of rotation vs vehicle speed graph which, inprincipal, corresponds to the diagram shown in FIG. 4. Further, in FIG.10, several torque vs time curves are shown to which curves variouscomponents of the drive train 1 can be subjected during a change of theratio in the range group 9 from the ratio stage “low” to the ratio stage“high”. Additionally in the FIG. 11 a plurality of rotational curves ofindividual components of the drive train 1 are shown in accord with FIG.1, during the ratio change in the range group 9 plotted against theshifting time t.

With the aid of the diagrams presented in FIGS. 9 to 11, in thefollowing a procedure for the control of the drive train 1 is describedwherein a change of the ratio of the range group 9 from the ratio stage“low” to the ratio stage “high”, due to optional vehicle speed, can becarried out with very short traction loss interruptions.

As can be seen in FIG. 9, at a particular point in time, namely in thiscase at time point T₀, the driver of the vehicle chooses the ratio stage“high” in the range group 9 on the shift-selector 27, wherein the ratiostage “low” has been in use up to this time. If the driver should havechosen the ratio stage “low”, if this has already been closed in therange group 9, then the driver's desired demand would be ignored in thecontrol apparatus of the drive train 1.

Upon the input of the driver's demand into the control apparatus of thedrive train 1, the control apparatus reduces the drive moment of themotor 2, which is reflected in the curve of the e-gas-moment m_(mot-e)as seen graphically in FIG. 10.

The drive train 1 is relieved of load via the reduction of the drivemoment of the motor 2 whereby, simultaneously, the torque m₂₄, withwhich the first shifting element 24 of the range group 9 is subjected,drops to zero. If the first shifting element 24 is full relieved ofload, then the first shifting element 24 is released, by way of whichthe neutral condition is established in the range group 9. The firstshifting element 24, which is constructed as a dog clutch, is made toopen by way of an electric motor in the range group 9. The opencondition of the first shifting element is determined by way of aposition sensor, which is not further described here. A signal of thepositioning sensor is processed by the control apparatus and shiftingelements of the automatic transmission 8, which are to be closed, andwhich the elements co-act in the automatic transmission 8 in countershifting which corresponds to shifting in the range group 9, and theelements are directed by the control apparatus.

The advantages of the method whereby, with a change of the ratio of therange group 9, a corresponding counter shifting takes place in theautomatic transmission 8 and does this without a change in the velocityv_(fzg) of the vehicle, are clarified in FIG. 8 by arrows 28, 29. At achange of the ratio of the range group 9 from “low” to “high” when thenautomatic transmission 8 is in the shifting mode “A6”, if a countershift in the automatic transmission 8 into the ratio “A3” occurs then amerging speed of rotation of the motor 2 of the new gear of themulti-group transmission 4 deviates considerably less from the speed ofrotation n_(mot) of the motor 2 at the ratio “A6L” of the multigrouptransmission 4, than would be the case if this were done without countershifting in the automatic transmission 8.

The merging speed of rotation n_(mot) the motor 2, which would beshifted into without a corresponding counter shift in the automatictransmission 8, is indicated by the additional arrow 29 in FIG. 8. Thislarge cross-over of speed of rotation is disadvantageous for the comfortof driving, since a compensating time, while the speed of rotation ofthe motor 2 to the new speed, i.e., a connecting speed of rotation isachieved, is much longer than is the case with lesser speed of rotationdifferences. The disadvantage arises during compensation time from thefact that the drive train 1 is relieved of duty and the shifting causesa break in the delivery of tractive force which, under certaincircumstances, causes a continuation of existing travel upward on asteep incline to be impossible.

After the removal of load from the drive train 1 and correspondingly,also from the first shifting element 24 of the range group 9, the torqueof the motor 2, i.e., e-gas-moment m_(mot-e), is held constant and in asubsequent control phase, is adjusted in such a manner as shown in FIG.10 that, in accord with the torque m_(mot) of the motor 2 as well aswith the speed of rotation of the same, namely n_(mot), and also thenumber of revolutions n_(mot) the motor 2, a synchronization is made ofthe second shifting element 25 of the range group 9. This allows a newratio to be set in the closable shifting element of the automatictransmission 8.

Torque curves (vs time) are shown in FIG. 10, corresponding to speed ofrotation curves (vs time) for the individual components of the drivetrain 1 are shown in FIG. 11. At a point of time T₀, at which a driver'sdemand for a change in a ratio in the range group 9 is made, namely, achange from the ratio “low” to the ratio “high”, which the driveractuates by the selector-switch 27, in accord with the demand, theshifting begins in the multi-group transmission 4 which calls for achange of the speed of rotation, i.e., a change of the curves of theindividual speeds of rotation of those elements which are to co-act inthe shifting of the drive train 1.

In order to bring about a change from the motor 2 speed of rotationn_(mot) in the least possible time from the speed of rotation of thegears at the instant T₀ for the multi-group transmission 4, asoriginally set by the driver, to the synchronized connective speed ofrotation of the gear of the multi-group transmission 4 now selected, acapability of transfer of the engaged and disengaged shifting elementsof the automatic transmission 8 is enacted in such a manner that themotor 2 assumes the speed of rotation n_(mot), as is seen in the curvepresented in FIG. 11.

At the point in time T₁, the speed of rotation n_(mot) of the motor 2attains the connective rotational speed n_(mot-a), which previously wascomputed in the control apparatus in accord with the “new” ratio of themulti-group transmission 4 and the actual vehicle travel speed, namelyv_(fzg). By means of this, the vehicle travel speed v_(fzg), isdetermined via ABS sensors (not further described) available in thevehicle or by other appropriate apparatuses contained in the vehicle.

The motor 2 speed of rotation n_(mot) be brought essentially morequickly to the connection rotational speed _(nmot-a) with thepreselected procedure than this can be accomplished with a soleadjustment of the e-gas-moment. In this way, the motor 2, in the presentcase, is advantageously braked by an increase of the transfer capabilityof the closable shifting elements of the automatic transmission 8. Theclosable shifting elements of the automatic transmission 8 are operatingin a so-called “slip-phase” and brake the motor 2 at the correspondingconnection speed of rotation of the motor 2 in the shortest possibletime. The control of the shifting elements, which are to be shifted, ofthe automatic transmission 8, is carried out in such a manner that by acontrolled mutual frictional contacting of the shifting elements, atransfer capability of the required value is made available.

At the instant T₂, the closable shifting elements of the automatictransmission 8 and the second shifting element 25 of the range group 9are synchronous, so that the closable shifting elements of the automatictransmission 8, as well as the second shifting element 25, can be closedand the flow of force from the motor 2 to the output of the vehicle isre-established. At the same time, the automatic transmission 8 openableshifting elements are, indeed, opened and thus taken out of the flow offorce of the drive train 1.

By means of an additional position sensor, the through shifting of thesecond shifting element 25, which is constructed as a dog clutch, isrecognized and the drive moment of the motor 2, i.e., the e-gas-momentm_(mot-e), is matched to the demanded drive moment m_(mot-f) so thattravel continues on with corresponding drive speed of rotation andtorque of the motor 2.

The above described synchronization of the shifting elements of theautomatic transmission 8 and the range group 9, which take part in theshifting of the multi-group transmission 4, form the basis of the speedof rotation curves shown in FIG. 11, namely n₁₃, n₁₅, n₁₆, n₁₇, n₁₈,n₂₂, and n₂₃. The point of time T₀ marks the beginning of the shiftingphase in the multi-group transmission 4. In this application, contraryto the description accompanying FIG. 6, the shifting is not an automatedshifting, but is executed in accord with a demand at the driver'soption. With the generation of the driver's optional demand for theshifting into the ratio “low” in the range group 9, a capability oftransfer of the shifting element of the automatic transmission 8 is soadjusted that the speeds of rotation n₁₃, n₁₅, n₁₈, n₁₉, and the motorspeed of rotation n_(mot) are all reduced. The speed of rotation n₂₃ ofthe planetary gear carrier 23 of the range group remains essentiallyunchanged in this operation.

The reduction shown in FIG. 10 of the motor torque n_(mot) by thereduction of the e-gas-moment m_(mot-e) leads to a load relief of thefirst shifting element 24 of the range group 9, so that this can beopened quickly after the point in time T₀, and the speed of rotation n₂₂of the internal gear 22 of the range group 9 becomes greater with slowlyincreasing shifting time t while approaching the speed of rotation n₂₃of the planetary gear carrier 23 of the range group 9.

From the point in time designated as T₁ at which point the speed ofrotation n_(mot) of the motor 2 has already reached the connectinglymatched speed of rotation n_(mot-a), the transfer capability of theshifting element of the automatic transmission 8 is so adjusted that thespeeds of rotation n₁₅, n₁₇, n₁₈, n₁₉ are further reduced and the speedof rotation n₁₆ of the second sun gear 16 of the second planetary gearset 14 increases to approach the speed of rotation n₂₃ of the planetarycarrier 23 of the range group 9.

At this point in time T₂, the speeds of rotation n₁₅, n₁₆, n₁₇, n₁₈, n₁₉and n₂₂ are equal to the speeds of rotation n₁₃ and n₂₃, so that theclosable shifting elements of the automatic transmission 8 as well asthe second shifting element 25 of the range group 9 are synchronized andcan be closed. At the point in time T_(ds), the through shifting of thesecond shifting element 25 of the range group 9 is determined by aposition sensor and the procedure of the shifting of the multi-grouptransmission 4 is concluded.

The two above described embodiment examples indicate the advantageoussituation that mechanical synchronization in the range group 9 can beeliminated, whereby a reduction of traction-moment and an accompanyingreduction of fuel consumption would take place. Additionally, a resultof the no longer necessary mechanical synchronization, savings inweight, engine space and cost advantages become available with theinvented dog-clutch equipped range group.

Moreover, with the invented method, considerable shortening of theelapsed time of interruptions in traction can be gained during thechanges of the ratios in the range group 9 as compared to suchtime-saving with conventional methods. In the embodiment example asshown in the FIGS. 2 to 5, the change of the ratio in the range group 9is automatic and the driver is thus relieved of this duty.

With the carrying out of the invented method in accord with FIGS. 6 to10, a change of the ratio in the range group with the generation of anoptional demand by the driver for the changing of the ratio in the rangegroup at any travel speed of the vehicle can be executed with minimaltraction interruption time, whereby simultaneously in accord with thegear change in the multi-group transmission, a matching motor rotationalspeed to the new ratio of the multi-group transmission is possible,whereby driving comfort and safety, especially upon steep inclines, aresubstantially improved.

REFERENCE NUMERALS

-   1 Drive train-   2 Driving machine, i.e. “motor”-   3 Start-up element-   4 Multi-group transmission-   5 Output drive shaft-   6 Hydrodynamic torque converter-   7 Controlled converter coupling-   8 Automatic transmission-   9 Range group-   10 First planetary gear set-   11 Internal gear of the first planetary gear set-   12 Sun gear of the first planetary gear set-   13 Planetary gear carrier of the first planetary gear set-   14 Second planetary gear set-   15 First sun gear of the second planetary gear set-   16 Second sun gear of the second planetary gear set-   17 Common internal gear of the second planetary gear set-   18 First planetary gear carrier of the second planetary gear set-   19 Second planetary gear carrier of the second planetary gear set-   20 Transmission housing-   20A Transmission housing of the range group-   21 Sun gear of the range group-   22 Internal gear of the range group-   23 Planetary gear carrier of the range group-   24 First shifting element of the range group-   25 Second shifting element of the range group-   26 Selection lever for the automatic transmission-   27 Shift-selector-   28 Arrow-   29 Arrow-   30 Circuit-   A-E Shifting elements of the automatic transmission-   “D” Drive, forward direction-   “A1”-“A6” Ratio of the automatic transmission-   H Ratio “high” of the range group-   L Ratio “low” of the range group-   m Moment-   m_(mot-e) e-gas-moment-   m_(mot-f) Driver moment-   m₂₄ Curve of the torque of the first shifting element of the range    group-   m₂₅ Curve of the torque of the second shifting element of the range    group-   n Speed of rotation-   “N” Neutral-   n_(mot) Torque of the motor-   n_(mot-a) Connecting speed of rotation (matched speed of rotations)-   “O” Off road, forward travel-   “P” Parking-   “R” Reverse-   “t” Shifting time-   “T” A point in time, a particular instant-   T_(ds) Point of through-shifting-   v_(fzg) Vehicle travel speed-   I-III Ratio of the multi-group transmission-   III-L Ratio of the multi-group transmission (low)-   III-H Ratio of the multi-group transmission (high)-   IV-VIII Ratio of the multi-group transmission

1. A method for controlling a drive train (1) of a vehicle, especiallyan all-terrain vehicle having a prime mover (2), a multi-grouptransmission (4), an output means and a control apparatus for theregulation of the drive train (1), the multi-group transmission (4)comprising an automatic transmission (8) and a range group (9) connecteddownstream to the automatic transmission (8) in a direction of powerflow, the method comprising the steps of: changing a ratio of the rangegroup (9) by closing a first shifting elements (24, 25) of the rangegroup (9); synchronizing and opening a second shifting element (24, 25)of the range group (9); and automatically selecting a combination of aratio of the automatic transmission (8) that with the changed ratio ofthe range group (9) will achieve a predetermined ratio for themulti-group transmission (4) for all gear stages by means of asuperimposed operational strategy; wherein the ratio of the automatictransmission (8) is selected according to the superimposed operationalstrategy so that in combination with the ratio of the range group (9) achange in output rotational speed of the multi-group transmission isminimized for the predetermined ratio of the multi-group transmission,and wherein synchronization of the shifting elements (24, 25) of therange group is performed by synchronization of shifting elements (A-E)of the automatic transmission, and fulfilling a demand of a driver(m_(mot-f)) for alteration of the torque (m_(mot)) of the motor (2)during the change of the ratio of the range group (9) upon theconclusion any ratio change via a control apparatus.
 2. A method forcontrolling a drive train (1) of an all-terrain vehicle having a motor(2), a multi-group transmission (4), an output means and a controlapparatus, the multi-group transmission (4) comprising an automatictransmission (8) and a range group (9), the range group beingconnectedly situated after the automatic transmission (8) in a directionof power flow, the method for controlling the drive train (1) comprisingthe steps of: selecting a desired multi-group transmission (4) ratio,automatically selecting, by means of a superimposed operationalstrategy, a combination of a ratio of the automatic transmission (8) anda ratio of the range group (9) for achieving a selected ratio of themulti-group transmission (4) for all gear stages; wherein the ratio ofthe automatic transmission (8) is selected according to the superimposedoperational strategy so that in combination with the ratio of the rangegroup (9) a change in output rotational speed of the multi-grouptransmission is minimized for the predetermined ratio of the multi-grouptransmission, wherein the ratio of the multi-group transmission (4) iseffected by means of one of a combination of the ratio of the automatictransmission (8) and a ratio “low” of the range group (9) or by acombination of a ratio “high” of the range group (9) and a correspondingratio of the automatic transmission without substantially effecting thespeed of rotation (m_(mot)) of the motor (2), including synchronizingopening and closing of shifting elements (24, 25) of the range group (9)by and concurrently with synchronization of a shifting of shiftingelements (A-E) of the automatic transmission.
 3. The method forcontrolling a drive train (1) of an all-terrain vehicle as set forth inclaim 2, the method further comprising the step of shifting the rangegroup (9) between a high and low gear ratio when the multi-grouptransmission (4) attains one of the substantially equal first and secondtransmission ratio.
 4. The method for controlling a drive train (1) ofan all-terrain vehicle as set forth in claim 3, the method furthercomprising the step of shifting any necessary shifting elements of therange group (9) and the automatic transmission (8) independently of thespeed of rotation (n_(mot)) of the motor (2) during the step of shiftingthe range group (9) between the high and low gear ratio.
 5. The methodfor controlling a drive train (1) of an all-terrain vehicle as set forthin claim 2, the method further comprising the step of maintaining asubstantially constant speed of rotation (n_(mot)) of the motor (2)during a shift of the range group (9) between a high and low gear ratio.6. A method for controlling a drive train (1) of an all-terrain vehiclehaving a motor (2) connected via an output shaft (5) and a start upclutch to multi-group transmission (4) comprising an automatictransmission (8) and a range group (9) connected downstream from theautomatic transmission (8) in a direction of power flow, the method forcontrolling the drive train (1) comprising the steps of: providing afirst range of transmission ratios defining a first shifting strategyfor the multi-group transmission (8) and providing a second range oftransmission ratios defining a second shifting strategy for themulti-group transmission (4); forming each of the first and second rangeof transmission ratios according to a combination of a range group ratioin the range group (9) and an automatic transmission ratio in theautomatic transmission (8); and establishing a first transmission ratioin the first range of transmission ratios which is substantially equalto a second transmission ratio in the second range of transmissionratios, wherein an automatic transmission ratio in the automatictransmission is automatically selected for a given range group ratioaccording to the superimposed operational strategy so that a combinationof a ratio of the automatic transmission and a ratio of the range groupachieve a desired ratio of the multi-group transmission for all gearstages and wherein the automatic transmission ratio is selected so thatin combination with the range group ratio a change in output rotationalspeed of the multi-group transmission is minimized for the desired ratioof the multi-group transmission, and actuation of shifting elements ofthe range group are synchronized with and by synchronization ofconcurrent actuation of shifting elements of the automatic transmission.7. A method for shifting a range group (9) of a multi-group transmission(4) from a current range group (9) ratio to a new range group (9) ratiowherein the multi-group transmission (4) includes an automatictransmission (8), the range group (9) connected downstream to theautomatic transmission (8) in a direction of power flow, and a controlapparatus for the regulation of the multi-group transmission (4),comprising the steps of: selecting a new multi-group transmission (4)ratio, automatically selecting a new automatic transmission (8) ratioand a new range group (9) ratio according to a superimposed operationalstrategy so that a combination of the new automatic transmission (8)ratio and the new range group (9) ratio provide the new multi-grouptransmission (4) ratio, wherein the range group (9) ratio and theautomatic transmission (8) ratio are automatically selected according tothe superimposed operational strategy so that a change in themulti-group transmission (4) ratio is minimized, and automaticallyshifting the automatic transmission (8) to the selected automatictransmission (8) ratio, and concurrently automatically shifting therange group (9) to the selected range group (9) ratio, wherein asynchronization of shifting elements (24, 25) of the range group (9) isachieved by synchronization of shifting elements (A-E) of the automatictransmission (8), and wherein the shifting of the automatic transmission(8) and the range group (9) to the new automatic transmission (8) andrange group (9) ratios is independent of an input torque into theautomatic transmission.
 8. The method according to claim 7, furthercomprising the steps of changing the ratio of the range group (9) andaltering the ratio of the automatic transmission (8) at an operationalpoint of the drive train (1) wherein a change of ratio of themulti-group transmission (4) does not take place.
 9. The methodaccording to claim 7, further comprising the step of demanding one of anarrow ratio-range and a wide ratio-range of the multi-grouptransmission (4) and creating the wide ratio-range according to a changein the ratio of the range group (9).
 10. The method according to claim7, further comprising the step of demanding one of a narrow ratio-rangeand a wide ratio-range from the multi-group transmission (4) to becarried out by a change of the ratio of the automatic transmission (8).11. The method according to claim 7, wherein a speed of rotation(n_(mot)) of the motor (2) remains essentially unaffected, when theratio of the range group (9) is changed.
 12. The method according toclaim 7 wherein, further comprising the step of executing a driverdemand (m_(mot-f)) for a change of motor torque (m_(mot)) following thechange of the ratio of the range group (9).
 13. The method according toclaim 7, further comprising the step of synchronizing the range group(9) during a change in a ratio of the range group (9) by actuation of ashifting element of the automatic transmission (8).
 14. The method forshifting a range group (9) of a multi-group transmission (4) of claim 7,wherein: according to the superimposed operational strategy, the newautomatic transmission (8) ratio is selected to minimize a torque leveltransferred through the automatic transmission (8) and to minimize arotational speed difference across the range group (8).
 15. The methodfor shifting a range group (9) of a multi-group transmission (4) ofclaim 7, further comprising the step of: maintaining a currentrotational input speed to the automatic transmission (8) at a currentvalue until the shifting of the automatic transmission (8) and the rangegroup (9) to the new automatic transmission (8) and range group (9)ratios is completed.
 16. The method for shifting a range group (9) of amulti-group transmission (4) of claim 7, further comprising the step of:reducing a current rotational input input torque to the automatictransmission (8) from a current value until the shifting of theautomatic transmission (8) and the range group (9) to the new automatictransmission (8) and range group (9) ratios is completed.
 17. The methodfor shifting a range group (9) of a multi-group transmission (4) ofclaim 7, wherein: the shifting of the automatic transmission (8) and therange group (9) to the new automatic transmission (8) and range group(9) ratios is completed in less than 0.2 seconds.